1. Field of the Invention
The present invention relates to fabric materials and more particularly to a conductive fabric with high flex resistance.
2. Description of Related Art
The conductive fabric provided with a conductive yarn capable of passing electric current in the fabric is used to provide a heater, a sensor, or an antenna or the like integrally formed in or with the fabric such as woven fabric, knitted fabric, and nonwoven fabric. For example, U.S. Pat. No. 5,927,060 discloses the conductive yarn referred to as a covered yarn that includes a polyester core yarn spirally wrapped with metal wires. A stainless steel wire is preferably used as the metal wire in such conductive yarn because the stainless wire has high tensile strength and corrosion resistance in comparison with other metal wires.
The conductive fabric is bent into various shapes in use. When the conductive fabric is used as a seat material of a vehicle seat which includes a heater and a pressure sensor, for example, a passenger repeatedly sits on and stands up from the conductive fabric or moves the buttocks in various directions with being seated. At this time, the conductive fabric is bent in upward and downward directions, forward and backward directions, and in various directions. In a case where the conductive fabric is used as clothing, the conductive fabric is bent through movements of a body during the donning and doffing processes or under wearing conditions. The metal wire forming the conductive fabric has a small diameter, and therefore when the metal wire is repeatedly bent, a break in the metal wire may occur due to metal fatigue. In the case of the break in the metal wire, electrical resistivity increases at the break, and the functions of the conductive fabric are impaired. When the metal wire breaks during the passage of electric current, the electrical resistivity may increase without user being aware of the break, and a sudden temperature rise may occur. In addition, the break in the metal wire may occur not only during the use of the conductive fabric but also in dyeing processes. This is because the fabric needs to be strongly rubbed during the dyeing processes. As described above, if there is a possibility that the metal wire breaks in the dyeing processes or under usage conditions, the conductive fabric may become unreliable.